The present invention relates to curable epoxy resin formulations useful for applications in which adhesion to metal substrates is important. In particular, this invention relates to curable epoxy resin compositions useful for applications such as metal coating compositions, composite materials, electrical laminates, electronic components, and circuit boards, and processes for making and using the same.
Thermoset resins are often used in coating compositions, composite materials, and electronic devices where strong adhesion to a metal substrate is important. While epoxy resins generally provide good adhesion to such substrates, there is room for improvement, especially in applications in which strong adhesion is important to the performance of the end product.
While the introduction of functional groups into resin compositions is known to increase adhesive strength, that approach tends to reduce other performance properties of the resin composition and tends to introduce processability problems. Simultaneously improving adhesion to metals while maintaining a high glass transition temperature, Tg, and high thermal stability, Td, has proven difficult.
In addition, viscosity control is an important issue in the processing of prepregs used to make composite materials and electrical laminates. The viscosity decrease of the resin in the prepreg during heating must be sufficient to permeate the composite material and make good contact with any materials with which the resin should adhere and yet should be sufficiently compensated by sufficient advancement of the resin to prevent an excessive amount of the resin from flowing out of the prepreg during pressing of the prepreg.
These and other problems relating to thermoset resin compositions are solved by the present invention described below.